Wireless Ad Hoc Network for Dublin:
A Large-Scale Ad Hoc Network Test-Bed
by Stefan Weber, Vinny Cahill, Siobhan Clarke and Mads Haahr
The migration of wireless networks from hotspots to multihop ad hoc networks is the first step towards self-organized global routing. The WAND project is deploying a large-scale test-bed for ad hoc network protocols in the centre of Dublin to facilitate research in this emerging discipline.
Wireless networks are rapidly becoming common place; upcoming technologies support wireless communication on chip-sets; new laptops have built-in WiFi cards; hotspots are being installed in airports, hotels and coffee shops; and offices are converting their existing local area networks to wireless to allow their workers take advantage of mobility. Soon numerous embedded devices - that form the heart of the ubiquitous computing revolution - will join this domain and increase the number of participants exponentially. Existing network architectures that use dedicated central nodes to coordinate the communication between participants will become more and more infeasible as the number of participants increases by orders of magnitude and where devices will more likely converse with one another in an ad hoc fashion.
Ad hoc networks present the next great challenge for distributed systems research. In an ad hoc network, the participants are used to route communication traffic from senders to receivers. Every participating node in these networks executes a routing algorithm that allows messages to be directed towards the next node along a route to the receiver. Protocols that support communication in ad hoc networks have to take into account the mobility of the participants and the variation in the connectivity between associated parties. New applications in these ad hoc communication scenarios can take advantage of the peer-to-peer characteristics of the network and offer location-based services that address specific communities of users.
To support research in this area the Distributed Systems Group in the Department of Computer Science at Trinity College Dublin, in collaboration with Media Lab Europe (MLE), is deploying WAND, the Wireless Ad hoc Network for Dublin, as a large-scale test-bed for ad hoc network protocols and applications. The network will cover the centre of Dublin along a 2km route from Trinity College to MLE. This area will be seeded with a number of custom-build wireless-enabled embedded PCs. These PCs are 3x3x6 inch containers that accommodate a stack of PC/104 boards, WiFi PCMCIA cards, and a set of antennae. The embedded PCs will be hosted in apartments and shops, on traffic lights, and in phone kiosks along the route to provide a minimum level of connectivity.
The embedded PCs form a sparse population of wireless network nodes. This sparse coverage is constantly available and the embedded PCs can be configured to create a variety of network models. The test-bed can be further populated through the introduction of mobile nodes such as laptops, PDAs, and other mobile devices with wireless connectivity. This ability to be configured in various ways and to be populated sparsely or densely enables researchers to develop and investigate protocols and applications that are specific to the area of ad hoc networking in various scenarios.An example of such an investigation is the examination of routing protocols for ad hoc networks. The routing of messages in an ad hoc network represents a difficult problem that is addressed by several mature or recently proposed routing protocols. These protocols have distinct advantages and disadvantages and it is important to determine the exact circumstances under which each of these protocols represents a good choice. The WAND test-bed offers a unique opportunity to explore the behaviour and performance of routing protocols in a real-life environment and to investigate requirements that are necessary to provide services such as location-based information or quality-of-service provision.
Another area of research that is investigated with the help of the WAND test-bed concerns the adaptation of applications to wireless ad hoc networks. Existing applications are rarely designed to take advantage of additional information and services that are offered by ad hoc networks. The applications range from peer-to-peer file sharing mechanisms that facilitate the exchange of data in ad hoc networks to location-based services that provide data to users depending on their physical position in the network.
An example of the applications that will be explored with the help of the WAND test-bed is communication between vehicles. This application will help mobile network nodes like cars, buses, and trucks communicate with one another and with static network nodes such as traffic lights, bus shelters, and traffic cameras. Mobile participants may inform one another about obstacles on the roads, actions that are going to be taken to avoid obstacles, or the routes of emergency services vehicles. Static nodes may provide information about the state of the traffic in an area and exploit information from mobile nodes such as the number of passengers or the estimated arrival time of buses.
The WAND test-bed offers researchers a unique opportunity to investigate low-level mechanisms such as routing protocols and low level services, as well as user-level applications in a real-life environment that reflects all the randomness and unpredictability that is extremely difficult to be reproduced with simulation.
Stefan Weber, Trinity College Dublin, Ireland
Tel: +353 1 608 1543